KR20020084165A - Novel blend polymer membranes for use in fuel cells - Google Patents

Abstract

The invention relates to novel blend polymer membranes that contain a functional polymer on the basis of sulfonated aryl polymers, a reinforcement polymer on the basis of aminated or nitrated polyether sulfones and/or polyether ether sulfone and a softener. The invention further relates to the use of the inventive membranes as polymer electrolyte membranes in fuel cells, especially in low-temperature fuel cells.

Description

Novel blend polymer membranes for use in fuel cells

The present invention relates to novel polymer blend membranes based on sulfonated aromatic aryl polymers and their use as polymer electrolyte membranes in fuel cells, especially low temperature fuel cells.

Fuel cell technology has many potential uses in aerospace, road transport, submarines and fixed energy supply. In particular, automobiles driven by fuel cells are expected to improve environmental protection in the transportation sector. However, apart from some technical problems, there are certain problems with the "cost / benefit ratio". A significant reduction in fuel cell costs is absolutely necessary. Therefore, there is a great interest in the development of inexpensive components that provide the required performance for fuel cells.

Polymer electrolyte membrane fuel cells typically consist of a cell unit comprising a terminal lead, a gas distributor, an electrode and a polymer electrolyte membrane. The electrode typically comprises platinum as a catalyst. Such fuel cells operate using gaseous hydrogen or methanol (DMFC = direct methanol fuel cell).

For use in fuel cells, the membrane must not only have sufficient chemical and mechanical stability and high proton conductivity, but also must be less expensive to manufacture. For this reason, low cost starting materials and cost with excellent properties for functionalization Low cost membrane fabrication is a decisive factor.

The perfluorinated cation exchange membranes that have been used to date show a serious deficiency in this respect. Apart from the complex manufacturing process and recycling issues, this material is very expensive and has a high methanol permeability which greatly limits the use of these membranes in methanol fuel cells.

Further membrane materials are modified heat resistant polymers such as polybenzimidazole (PBI) and polyether sulfone (PES). For this purpose, PBI is usually treated with phosphoric acid (Wainright, JS; Wang, J.-T .; Savinell, RF; Litt, M .; Moaddel, H .; Rogers, C .; Acid Doped Polybenzimidazoles, A New Polymer Electrolyte; The Electrochemical Society, Spring Meeting, San Francisco, May 22-27, Extended Abstracts, Vol. 94-1, 982-983 (1994)]. Phosphoric acid molecules are first attached to the polymer by hydrogen bonding, followed by protonation of the imidazole group of the membrane. However, there is a problem that phosphoric acid is gradually removed from the PBI matrix along with the water produced during operation of the fuel cell. Moreover, PBI-phosphate membranes have very low elastic modulus, which is why unsatisfactory membrane stability of fuel cells is expected.

EP-A-574791 and in Nolte, R .; Ledjeff, K .; Bauer, M. and Mulhaupt, R .: Partially Sulfoned poly (arylene ether sulfone) -A Versatile Proton Conducting Membrane Material for Modern Energy Conversion Technologies; Journal of Membrane Science 83, 211-220 (1993) describes low cost alternatives based on sulfonated aryl polymers such as sulfonated PEEK, PEK and PES. However, cation exchange membranes made of such sulfonated aryl polymers tend to swell severely at elevated temperatures. This greatly limits the suitability of such membranes for use in fuel cell systems.

German Patent Publication No. 4422158, German Patent Publication No. 198 13 613, German Patent Publication No. 198 17 376 and German Patent Publication No. 198 17 374 are polymers based on sulfonated aryl polymers with improved mechanical stability. Blend membranes are described.

An important prerequisite for such blends is the miscibility of the selected materials. To this end, only substances with similar chemical structures are mixed, in which case only the specific interactions between polymers with complementary groups occur, for example, the production of multiple salts from polyacids and multiple bases, the formation of hydrogen bonds and the like. Etc.

An important advantage of polymer blend membrane development is that the structure or properties of the membrane can be maximally utilized in the desired manner by varying the blend components and mixing ratios.

In this way, German Patent Publication No. 4422158 describes a polymer blend membrane comprising sulfonated polyether ketone (PEK) and unmodified polyether sulfone (PES). These two components can be mixed perfectly with each other, which can be attributed to their very similar chemical structure and polarity (ion-dipole interaction) of the PES. However, such interactions due to structural similarity still appear insufficient, so there is a risk that these membranes will swell very heavily at elevated temperatures in terms of the ion exchange capacity required for operation of the fuel cell.

German Patent Publication No. 4422158 discloses sulfonated PEK, PES, polyvinylpyrrolidone (PVP) and polyglycol dimethyl ether (PG), which show improved water uptake but no quantitative data are reported. A three or four component blend is described.

German Patent Publication No. 198 17 374 discloses sulfonated aryl polymers (PEEK and PSU) covalently crosslinked by proton transfer from sulfonated aryl polymers to PBI (eg, PEEK-SO ₂ -OHN-PBI) and Blends of polybenzimidazole PBI have been described. This crosslinking occurs even when at room temperature in a solvent such as N-methylpyrrolidone (NMP) as a result of insoluble polymer electrolyte complexes. In order to produce a polymer blend membrane, the sulfonated aryl polymer must be converted to soluble salt form. This additional step complicates the manufacture of the membrane.

The interaction between the PBI and the aryl polymer is so strong that high homogeneity is created between the crosslinking region in the membrane, the gel phase swollen by water and the polymer matrix. This can cause internal stress of the membrane which can degrade the mechanical stability of the membrane.

The prior art describes polymer blend membranes comprising sulfonated aryl polymer PEEK or PSU with aminated polysulfone (PSU). In this topic, Cui, W in Entwicklung und Charakterisierung von Kationenaustauscher-Membranen aus Arylpolymeren (VDI publishers; ISBN 3-18-359603-2), shows that aminated polysulfones are weak polybasics and therefore It is described that base mixtures can be produced in solution. Both ionic interactions and hydrogen bonds, ie ring structures with physical crosslinks, are present between the blend components. When tested in PEMFC and DMFC, this polymer blend membrane had a current density of 1.0 to 1.2 A / cm ² at a voltage of 0.7 V in H ₂ / O ₂ -PEMFC and a 0.4 to 0.6 A current density in air / H ₂ -PEMFC. / cm ² . In DMFC, this film also exhibits a UI curve comparable to Nafion-117, for example.

Given this background, the development of crosslinked polymer blend membranes by ionic interactions for use in fuel cells is promising for low temperature fuel cells.

It is an object of the present invention to provide an inexpensive polymer blend capable of producing a polymer electrolyte membrane of a fuel cell having at least the same or better performance than the prior art.

The polymer blends to be found should be able to match the properties of these membranes to the operating conditions of the fuel cell in the desired manner by varying the mixing ratio.

The object is a novel polymer blend based on modified polyether sulfones and polyether ether sulfones as reinforcing components as ionic interactions and sulfonated aryl polymers and plasticizers as functional polymers, for example aminated polyether sulfones and functional polymers. Can be achieved by the membrane.

The invention is based on at least one functional polymer (A) based on at least one aryl polymer containing sulfonic acid groups, at least one aminated polyether sulfone / polyether ethersulfone or nitrated polyether sulfones / polyether ether sulfones Providing a polymer blend membrane comprising at least one reinforcing polymer (B) which improves the stability of the membrane to swelling behavior as a result of its interaction with the functional polymer and at least one plasticizer (C) which reduces the brittleness of these polymers. .

The functional polymers used according to the invention are sulfonated aryl polymers, for example sulfonated PEEK (SPEEK), sulfonated PEK (SPEK), sulfonated PEEKK (SPEEKK), sulfonated PES (SPES) or sulfonated PEES ( SPEES).

According to the invention, the polymer blend membrane can be produced from PBI and modified polyether sulfones or modified polyether ether sulfones. This polymer blend membrane is functionalized by phosphoric acid like the PBI membrane.

Such aryl polymers,

, , And

Aromatic building blocks selected from the group consisting of

-CF _2- , -O-, , And

And a thermally stable linking unit selected from the group consisting of:

Sulfonation of aryl polymers is known. Thus, European Patent Publication No. 0574791 describes the preparation of sulfonated PEEK. EP 008895, EP 041780 and EP 0576807 describe the preparation of sulfonated PEKs. The preparation of sulfonated PEEKK is known from E. Muller in "Vernetzte PEEKK-Sulfonamide zur Trennung von Aliphaten / Aromaten-Gemischen" (Research work for a degree, 1995, Hoechst AG, Frankfurt / Main). EP0008894 and EP0112724 describe the preparation of polyether sulfones.

The sulfonation degree is preferably 0.1% to 100%.

The functional polymers used according to the invention are used in amounts of 30% to 99.9% by weight, based on the whole polymer.

Reinforcing polymers used according to the present invention,

or

Aminated polyether sulfones or polyether ether sulfones comprising structural units of wherein x is each independently 0,1,2,3 or 4

or

Is a nitrated polyether sulfone or polyether ether sulfone comprising a structural unit of wherein x is each independently 0, 1, 2, 3 or 4.

or

Particular preference is given to aminated polyether sulfones and polyether ethersulfones comprising structural units in the form.

or

Particular preference is given to nitrated polyether sulfones and polyether ether sulfones comprising structural units in the form.

The reinforcing polymers used according to the invention are used in amounts of 0.1% to 70% by weight, preferably 10% to 50% by weight, based on the whole polymer.

Ionic interactions between blend components (polyacid / polybase blend or polyacid / polyacid blend) can be expressed as follows:

PES-NH ₂ + polymer aryl _{-SO 3 H → PES- (NH 3} ) + - SO 3 - aryl polymer

PES-NO ₂ + aryl polymer _{-SO 3 H → PES- (NO 2} -H) + - SO 3 - aryl polymer

For example:

PES-NH ₂ + PES-SO ₃ H → PES- (NH ₃ ) ⁺ -SO ₃ -PES

PES-NO ₂ + PES-SO ₃ H → PES- (NO ₂ -H) ⁺ -SO ₃ -PES

Sulfonated polyether sulfones (PES-SO ₃ H) and nitrated PES (PES-NO ₂ ) are both polyacids, so they are thoroughly mixed with each other. The miscibility of PES-SO ₃ H with aminated PES (PES-NH ₂ ) is not critical because of the complete miscibility of the polyacid / polybase mixture. Here, PES-NH ₂ and PES-NO ₂ function as "polymer counterions" to strengthen the membrane. Although the ionic compound dissolves in water at elevated temperatures, the interaction remains due to the localization of the "polymer counterions" at that location. For this reason, membranes are primarily enhanced at elevated temperatures by these "polymer counterions", and secondary dissolution promotes ion transport. The membrane of the present invention thus has the properties at advantageous elevated temperatures required for the use of a fuel cell.

Polyether sulfones (PES) are commercially available and have high thermal and chemical stability and good mechanical stability. The polarity of the polymer promotes water absorption.

Processes for the preparation of nitrated and aminated polyether sulfones and nitrated and aminated polyether ether sulfones are described simultaneously in German Patent Application No. 10010002.3.

For the purposes of the present invention, plasticizers are substances which reduce the brittleness of membranes produced from polymer blends. Suitable plasticizers should be inert under conditions effective for fuel cells. Moreover, the plasticizer must be mixed and miscible with the functional polymer and the reinforcing polymer, and the same dipolar solvents such as dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) Or be soluble in N, N-dimethylacetamide (DMAC).

Particular preference is given to using linear polyvinylidene fluoride (PVDF) as the plasticizer. The components of the three component polymer blend membrane comprising the functional polymer, the reinforcing component and the plasticizer are miscible with each other due to hydrogen bonding, acid-base interactions and ion-dipole interactions. Physical crosslinking in the membrane also contributes. However, ion-dipole interactions between PVDF and modified aryl polymers are very weak. As the proportion of PVDF in the blend increases, phase separation occurs in the membrane. This causes the film to become optically cloudy.

The plasticizer content is up to 5% by weight, preferably from 0.001% to 3% by weight, in particular from 0.1% to 2% by weight, based on the entire polymer.

PVDF is commercially available and has excellent thermal and chemical stability. The chemical structure of PVDF is as follows:

The production of the three component polymer blend membrane of the present invention is likewise carried out by the process described below.

The preparation of the polymer blend membrane of the present invention is carried out as follows: A solution of a homogeneous polymer mixture comprising a sulfonated aryl polymer, aminated PES or nitrated PES and a plasticizer is poured onto a support and then spread with a doctor blade. To produce a film of uniform thickness. The solvent in the film is removed by evaporation, for example. Suitable solvents are, in particular, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) or N, N-dimethylacetamide (DMAC). The dried membrane is then separated from the support to condition the resulting membrane.

The present invention provides an economically advantageous polymer blend material; Starting polymers are inexpensive and the process of denaturing PES and PEES and the preparation of polymer blend membranes are simple.

The structure of the membrane and the properties of the membrane, such as conductivity and swelling of the membrane, can be adjusted depending on the application in which the membrane is to be used. Compared to membranes made of sulfonated aryl polymers, the polymer blend membranes of the present invention exhibit improved mechanical and thermal properties.

The polymer blend membrane of the present invention consists of one layer or a plurality of identical or different layers (multilayers) such as sulfonated aryl polymers and aminated polysulfones (a) and sulfonated aryl polymers and nitrated polysulfones (b). It can consist of two layers. Moreover, various multilayer membranes comprising at least two different layers selected from the group consisting of SPEK and NH ₂ -PES, SPEK and NO ₂ -PES, SPEK and NH ₂ -PES and a plasticizer, SPEK and NO ₂ -PES and a plasticizer It is included in the present invention.

The invention is illustrated by the following examples which do not limit the scope of the invention:

General way to characterize the membrane

Ion exchange capacity (IEC, meq / g): Potentiometric titration is used to measure the ion exchange capacity of the membrane.

Swelling (swe, wt%): The swelling of the membrane depends on the substrate, temperature and time. The specimen of the membrane is conditioned in water at a certain temperature for a certain time. Then the water content of the specimen is measured.

Conductivity (cond, mS / cm): The conductivity of the membrane is measured in water in a measuring cell at a temperature of 20 ° C. to 90 ° C. by impedance spectroscopy (Zahnler).

Mechanical properties (elastic modulus, N / mm ² ; elongation at break,%): To measure the mechanical properties of the membrane, the specimens were pretreated at 23 ° C., 50% humidity for 4 hours in a constant temperature humidity cabinet or the samples were subjected to 23 ° C. and Condition in water at 80 ° C. for 30 minutes. The specimens are then tested in a tensile tester (Zwick; pretension: 0.5 N; strain: 50 mm / min).

Thermal properties: The glass transition temperature and decomposition temperature of the membrane are measured by DSC and TGA (Mettler Toledo; 10 k / min).

Permeability: hydrogen, oxygen (gas pressure: 1 bar) and methanol permeability (32 g of methanol in 1000 g of H ₂ O) were used as membrane cells for S. Pauly / A. Measure as a function of temperature at Becker in Wiesbaden.

Comparison is made using commercially available perfluorinated polymer membranes with an IEC of 0.9 meq / g and a membrane swell (water, at 80 ° C.) swe of 31 wt%.

The mechanical properties of the films to be compared are shown in the following table:

Modulus of elasticity (N / mm ² ); In humid air; 23 ℃ 300N / mm ² Modulus of elasticity (N / mm ² ); In water; 80 ℃ 50N / mm ² Elongation at break (%); In humid air; 23 ℃ 175% Elongation at break (%); In water; 80 ℃ 255%

The permeability of the membranes to be compared is as follows:

Temperature (℃) Methanol / H ₂ O (g / m ² · d) (32 g / 1000 g H ₂ O) O ₂ permeability [cm ³ 50 μm / (m ² d bar)] H ₂ permeability [cm ³ 50 μm / (m ² d bar)] 40 61.9 2350 9880 60 151 5250 18800 80 333 8590 36300 100 674 14300 65200 120 1266 23300 113100

Examples 1 and 2

Polymer blend membranes comprising sulfonated PEEK (SPEEK) and aminated PES (NH ₂ -PES)

The ion exchange capacity of SPEEK is 1.73 meq / g. The substitution degree of NH ₂ -PES is 45% (1.9 meq / g). Polymer blend membrane TE-4 comprises 90% SPEEK and 10% NH ₂ -PES, TE-5 comprises 85% SPEEK and 15% NH ₂ -PES.

The data showing the characteristics of the film is shown below:

Calculated IEC: TE-4: IEC = 1.56 meq / g; TE-5: IEC = 1.47meq / g

Swelling of the membrane (80 ° C .; 48 h): TE-4: swe = 182.7 wt%; TE-5: swe = 83.8 wt%

conductivity T (℃) TE-4 (mS / cm) TE-5 (mS / cm) 23 64.6 28.9 30 73.6 34.4 40 85.5 40.8 50 97.3 47.6 60 108.9 53.8 70 120.3 59.2 80 131.4 63.6

Mechanical properties TE-4 TE-5 Modulus of elasticity (N / mm ² ); In humid air; 23 ℃ 1717.3 1212.5 Modulus of elasticity (N / mm ² ); In water; 80 ℃ 348.6 492.9 Elongation at break (%); In humid air; 23 ℃ 20.4 39.5 Elongation at break (%); In water; 80 ℃ 275.3 268.8

The permeability of the membrane TE-5 is 2.35 [g. 50 [mu] m / (m ² · d)] at 40 deg.

Hydrogen permeability and oxygen permeability are shown in FIG. 1 as a function of temperature (TE-5):

Examples 3 and 4

Polymer blend membrane comprising sulfonated PEEKK (SPEEKK) and aminated PES (NH ₂ -PES)

The ion exchange capacity of SPEEKK is 1.65 meq / g. The substitution degree of NH ₂ -PES is 45% (1.9 meq / g). Polymer blend membrane TE-8 comprises 90% SPEEKK and 10% NH ₂ -PES, TE-9 comprises 85% SPEEKK and 15% NH ₂ -PES.

The data showing the characteristics of the film is shown below.

Calculated IEC: TE-8: IEC = 1.49 meq / g; TE-9: IEC = 1.40meq / g.

Swelling of the membrane (80 ° C .; 48 h): TE-8: swe = 137.4% by weight; TE-9: swe = 95.2 wt%

conductivity T (℃) TE-8 (mS / cm) TE-9 (mS / cm) 23 45.4 28.0 30 54.7 34.0 40 64.0 40.1 50 73.4 46.3 60 82.6 52.3 70 91.6 58.4 80 99.5 63.8

Mechanical properties TE-8 TE-9 Modulus of elasticity (N / mm ² ); In humid air; 23 ℃ 907.8 1181.4 Modulus of elasticity (N / mm ² ); In water; 80 ℃ 442.3 486.0 Elongation at break (%); In humid air; 23 ℃ 11.6 17.6 Elongation at break (%); In water; 80 ℃ 230.2 190.1

The methanol permeability of the membrane TE-8 is 4.11 [g. 50 [mu] m / (m ² · d)] at 40 deg.

Examples 5-7

Polymer blend membranes including sulfonated PEK (SPEK) and nitrated PES (NO ₂ -PES)

The ion exchange capacity of SPEK is 2.13 meq / g. The degree of substitution of NO ₂ -PES is 50% (1.97 meq / g). Polymer blend membrane TE-23 comprises 80 wt% SPEK and 20 wt% NO ₂ -PES, TE-24 comprises 75 wt% SPEK and 25 wt% NO ₂ -PES, TE-25 Comprises 70% by weight SPEK and 30% by weight NO ₂ -PES.

The data showing the characteristics of the film is shown below.

Calculated IEC: TE-23: IEC = 1.70 meq / g; TE-24: IEC = 1.60meq / g, TE-25: IEC = 1.49meq / g.

Swelling of the membrane (80 ° C. in water): TE-23: swe = 99% by weight; TE-24: swe = 68% by weight, TE-25: swe = 47% by weight.

Mechanical Properties of TE-25 Modulus of elasticity (N / mm ² ); In humid air; 23 ℃ 2319.1 N / mm ² Modulus of elasticity (N / mm ² ); In water; 80 ℃ 402 N / mm ² Elongation at break (%); In humid air; 23 ℃ 24.2% Elongation at break (%); In water; 80 ℃ 219.3%

Examples 8-10

Polymer blend membrane comprising sulfonated PEK (SPEK) and aminated PES (NH ₂ -PES)

The ion exchange capacity of SPEK is 2.13 meq / g. The substitution degree of NH ₂ -PES is 45% (1.9 meq / g). Polymer blend membrane TE-1 comprises 85 wt% SPEK and 15 wt% NH ₂ -PES, TE-2 comprises 80 wt% SPEK and 20 wt% NH ₂ -PES, TE-3 Comprises 75% SPEK and 25% NH ₂ -PES.

The data showing the characteristics of the film is shown below.

Calculated IEC: TE-1: IEC = 1.82 meq / g; TE-2: IEC = 1.71 meq / g, TE-3: IEC = 1.61 meq / g.

Swelling of the membrane (80 ° C. in water): TE-1: swe = 167.2 wt%; TE-2: swe = 122% by weight, TE-3: swe = 70.4% by weight.

conductivity T (℃) TE-1 (mS / cm) TE-2 (mS / cm) TE-3 (mS / cm) 23 115.8 91.4 68.6 30 135.8 107.5 81.4 40 155.5 123.6 94.4 50 174.8 139.3 107.1 60 193.2 154.3 119.4 70 210.9 168.9 131.4 80 227.9 182.3 141.9

Mechanical properties TE-1 TE-2 TE-3 Modulus of elasticity (N / mm ² ); In humid air; 23 ℃ 2020.8 2420.6 2455.7 Modulus of elasticity (N / mm ² ); In water; 80 ℃ 52.7 134.3 357.9 Elongation at break (%); In humid air; 23 ℃ 30.8 23.4 10.3 Elongation at break (%); In water; 80 ℃ 290.6 301.8 249.1

Example 11

Tricomponent polymer blend membrane comprising 75 wt% SPEK (IEC = 2.13 meq / g), 25 wt% NO ₂ -PES (IEC = 1.96 meq / g) and 0.5 wt% PVDF (TE-29)

The data showing the characteristics of the film is shown below.

Measured IEC (acid-base titration): TE-29: IEC = 1.40 meq / g.

Swelling of the membrane (100 ° C., 72 hours in water): TE-29: swe = 162 wt%

Conductivity: 23 ° C .: 83.3 mS / cm; 30 ° C .: 99.0 mS / cm; 40 ° C .: 114.6 mS / cm; 50 ° C .: 130.1 mS / cm; 60 ° C .: 145.0 mS / cm; 70 ° C .: 159.4 mS / cm; 80 ° C .: 172.4 mS / cm.

Mechanical properties TE-29 Modulus of elasticity (N / mm ² ); In humid air; 23 ℃ 2051.9 Modulus of elasticity (N / mm ² ); In water; 80 ℃ 188.7 Modulus of elasticity (N / mm ² ); In water; 100 ° C, 72 hours 52.9 Elongation at break (%); In humid air; 23 ℃ 57.3 Elongation at break (%); In water; 80 ℃ 260.4 Elongation at break (%); In water; 100 ° C, 72 hours 112

Examples 12-19

Tricomponent polymer blend membrane comprising SPEK, NH ₂ -PES (IEC = 1.9 meq / g) and PVDF

Membrane number Material and Mixing Ratio IEC ^* (meq / g) SWE ^** (wt%) SWE ^*** (% by weight) Conductivity 80 ℃ (mS / cm) Conductivity 90 ℃ (mS / cm) TE-28 SPEK (2.13meq / g): 75% NH ₂ -PES (1.9meq / g): 25% PVDF: 0.5% 1.49 185 82.8 - TE-31 SPEK (2.13meq / g): 75% NH ₂ -PES (1.9meq / g): 25% PVDF: 1% 1.45 59 182 78 - TE-40 SPEK (2.13meq / g): 70% NH ₂ -PES (1.9meq / g): 30% PVDF: 1% 1.41 33.7 135.4 - - TE-41 SPEK (2.13meq / g): 70% NH ₂ -PES (1.9meq / g): 30% PVDF: 1.5% 1.42 27.7 128 53.6 74.7 TE-42 SPEK (1.83meq / g): 75% NH ₂ -PES (1.9meq / g): 25% PVDF: 1% 1.29 14 91 27.2 37.9 TE-43 SPEK (1.90meq / g): 75% NH ₂ -PES (1.9meq / g): 25% PVDF: 1% 1.44 16 69 - - TE-58 SPEK (1.90meq / g): 70% NH ₂ -PES (1.9meq / g): 30% PVDF: 1% 1.25 25.7 101.7 56 - TE-45 SPEK (1.64meq / g): 80% NH ₂ -PES (1.9meq / g): 20% PVDF: 0.5% 1.36 12 68 - - TE-70 SPEK (2.17meq / g): 80% NH ₂ -PES (3.8meq / g): 20% PVDF: 1% 1.64 - 204.7 80

^* Potentiometric titration with 0.1N NaOH. ^{** The} sample is heated in water at 80 ° C. for 72 hours. ^{*** The} sample is heated in water at 100 ° C. for 72 hours.

Mechanical properties:

TE-28 (23 ° C .; 50% humidity): Modulus of elasticity: 2689.7 N / mm ² ; Elongation at break: 23.7%.

The mechanical properties of the membrane in water at 80 ° C are shown in the table below.

Mechanical properties of the membrane (in water at 80 ° C) TE-28 TE-31 TE-40 TE-41 TE-42 TE-43 TE-58 TE-45 Modulus of elasticity (N / mm ² ) 420.4 428.8 502.3 480.9 806.6 824.6 701 995.6 Elongation at Break (%) 246.6 278.3 202.5 127.5 83 16.6 28.2 177.9

Mechanical properties of the membrane (100 ° C; 72 hours in water) TE-58 TE-70 Modulus of elasticity (N / mm ² ) 195.6 269.1 Elongation at Break (%) 128.3 231.7

The membrane is heated in 100 ° C. water for 72 hours.

Dynamic Mechanical Analysis:

Dynamic mechanical analysis quantitatively describes the toughness and attenuation behavior of test specimens by storage modulus (E ′), loss modulus (E ″) and dielectric loss (δ) as a function of temperature, time and frequency.

The measuring instrument is a dynamic mechanical analyzer DMA 242 (Netzsch-Geratebau GmbH).

The test conditions are as follows:

Measurement mode: tensile

Target amplitude: 30 μm (auto.)

Constant power: Prop .: 1.2

Power: 0.5N

Frequency: 1 Hz

Temperature range: -50 ° C to 300 ° C

Heating rate: 5K / min

Test piece width: 4mm

During the measurement, the membrane shrinks with increasing temperature. Further increase in temperature results in extension of the specimen. Above 200 ° C, the modulus of elasticity rapidly decreases. The specimen is stretched very much and the δ curve exceeds the maximum. The maximum value represents a glass transition temperature of 254 ° C. for TE-31 and TE-28. The results are shown in the table.

Storage modulus value (E ') as a function of temperature Membrane number E '(MPa); -30 ℃ E '(MPa); 0 ℃ E '(MPa); RT E '(MPa); 100 ℃ TE-31 2500 1800 1700 1900 TE-28 2700 2300 1500 2400 Nafion-115 ^* 1400 370 430 60

^* Comparative Example;

Membrane TE-31 and sulfonated, perfluorinated polymers such as Nafion-115 exhibit high attenuation behavior.

Thermal properties

The glass transition temperature is measured by DSC and the decomposition temperature is measured by TGA.

matter DSC TGA PVDF Tm = 148.5 ℃ 400 ℃ or more NH ₂ -PES Tg = 238.6 ° C. 320 ℃ or higher SPEK Tg = 181.7 ° C 300 ℃ or more Blend membrane Tg ₁ = 167.5 ° C; Tg ₂ = 227.3 ° C 300 ℃ or more

Transmittance of TE-42 Temperature (℃) Methanol / H ₂ O (g / m ² .d) (32 g / 1000 g H ₂ O) O ₂ permeability [cm ³ 50 μm / (m ² d bar)] H ₂ permeability [cm ³ 50 μm / (m ² d bar)] 40 2.5 293 3770 60 6.8 351 5380 80 16.1 417 7410 100 36 547 10250 120 67 763 14130

Membrane Testing in Direct Current Methanol Fuel Cells (DMFC)

Membrane TE-31:

Operating temperature: T = 100 ° C .;

Platinum content of the electrode: anode: 0.16 mg / cm ² , cathode: 0.62 mg / cm ² ;

Fuel cell: 1.0 M methanol; Methanol / air;

The current-voltage ratio: 430mV at 150mA / cm ^2, 200mA at ^{375mV / cm 2, 300mA / cm} 2 at 250mV.

This membrane shows very swelling in DMFC.

Membrane TE-41:

Operating temperature: T = 110 ° C .;

Platinum content of the electrode: anode: 0.16 mg / cm ² , cathode: 0.62 mg / cm ² ;

Fuel cell: 0.4 M methanol; Methanol / air; 3/3 bar;

Current / voltage ratio: 200 mA / cm ² at 468 mV, 300 mA / cm ² at 308 mV.

Membrane TE-42:

Operating temperature: T = 110 ° C .;

Platinum content of the electrode: anode: 0.16 mg / cm ² , cathode: 0.62 mg / cm ² ;

Fuel cell: 0.4 M methanol; Methanol / air; 3/3 bar;

Current / voltage ratio: 200 mA / cm ² at 463 mV, 300 mA / cm ² at 300 mV.

In a fuel cell, hydrogen is introduced into the positive cell and oxygen is introduced into the negative cell. Reduction of the membrane material by hydrogen may occur under the catalysis of platinum. In contrast, the oxidation of the membrane material by oxygen can likewise occur in the presence of platinum. In order to increase the chemical stability of the membranes in fuel cells, polymer blend membranes having a multilayer structure have been developed.

As such, a membrane having a double layer is composed of a total of four components. One of the bilayers contains sulfonated PEK, aminated PES and PVDF, while the other layer includes sulfonated PEK, nitrated PES and PVDF.

The PES-NO ₂ component is very stable for oxidation by oxygen, and PES-NH ₂ is very stable for reduction with hydrogen or methanol. This improves chemical stability.

The multilayer film is created in the following steps:

The membrane layer is first created by the method described in section 1.

⊙ Apply a thin film from the polymer solution to the layer. Evaporate the solution.

Condition the created bilayer.

Example 20

The double layer structure (TETD-1) is as follows:

Composition:

Upper layer: SPEK (2.13 meq / g): 76.5 weight%; NH ₂ -PES (1.9 meq / g): 22.5 wt%; PVDF: 1 wt%

Lower layer: SPEK (2.13 meq / g): 75% by weight; NO ₂ -PES (1.97 meq / g): 24% by weight; PVDF: 1 wt%

Membrane structure

3 shows the spectrum of a bilayer membrane. From the figure that the absorption band of the lower layer at 1535cm ^-1, 1346cm ^-1 and 908cm ^-1 it can be seen that belongs to the vibration of the NO ₂ -PES.

Conductivity of TETD-1 T (℃) 80 70 60 50 40 30 20 Upper side (mS / cm) 128.4 118.5 107.4 96.1 84.5 72.3 61.1 Lower side (mS / cm) 128.6 119.0 108.0 96.9 85.0 73.2 61.5

Mechanical Properties of TETD-1 TETD-1 Modulus of elasticity (N / mm ² ); In humid air; 23 ℃ 2222.1 Modulus of elasticity (N / mm ² ); In water; 80 ℃ 217.0 Elongation at break (%); In humid air; 23 ℃ 51.1 Elongation at break (%); In water; 80 ℃ 291.2

Claims (20)

One or more functional polymers (A) based on one or more aryl polymers containing sulfonic acid groups, based on one or more aminated polyether sulfones / polyether ether sulfones or nitrated polyether sulfones / polyether ether sulfones, A membrane comprising at least one reinforcing polymer (B) which improves the stability of the membrane against swelling behavior as a result of the interaction of and at least one plasticizer (C) which reduces the brittleness of the abovementioned polymers. The method according to claim 1 or 2, wherein the sulfonated aryl polymer is , , And An aromatic building block selected from the group consisting of -CF _2- , -O-, , And Membrane comprising a thermally stable connection unit selected from the group consisting of. The membrane of claim 1 wherein sulfonated polyether ether ketones, sulfonated polyether ketones, sulfonated polyether ether ketone ketones, sulfonated polyether sulfones and sulfonated polyether ether sulfones or PBIs are used as the sulfonated aryl polymers. . The membrane according to any one of claims 1 to 3, wherein the sulfonation degree of the sulfonated aryl polymer is 0.1% to 100%. The membrane according to any one of claims 1 to 4, wherein the sulfonated aryl polymer is used in an amount of 30% to 99.9% by weight based on the entire polymer. The method according to any one of claims 1 to 5, or A membrane using at least one aminated polyether sulfone and polyether ether sulfone comprising structural units of wherein x is each independently 0, 1, 2, 3 or 4. The method according to any one of claims 1 to 6, or A membrane using at least one nitrated polyether sulfone and polyether ether sulfone comprising structural units of wherein x is each independently 0, 1, 2, 3 or 4. The method according to any one of claims 1 to 7, or Membranes using aminated polyether sulfones or aminated polyether ether sulfones comprising structural units in the form as reinforcing polymers. The method according to any one of claims 1 to 8, or A membrane using nitrated polyether sulfones or nitrated polyether ether sulfones comprising structural units in the form as reinforcing polymers. The membrane according to any one of claims 1 to 9, wherein the reinforcing polymer used according to the invention is used in an amount of 0.1% to 70% by weight based on the whole polymer. The membrane of claim 1, wherein the plasticizer reduces the brittleness of the membrane resulting from the polymer blend. The membrane according to any one of claims 1 to 11, wherein the plasticizer is inert under conditions effective for the fuel cell. The membrane according to claim 1, wherein the plasticizer is mixed and miscible with the functional polymer and the reinforcing polymer. The method of claim 1, wherein the plasticizer is dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) or N, N-dimethylacetamide (DMAC). Membrane that is soluble in. The membrane according to any one of claims 1 to 14, wherein linear polyvinylidene fluoride (PVDF) is used as a plasticizer. The membrane according to any one of claims 1 to 15, wherein the plasticizer content is 5% by weight or less based on the entire polymer. The membrane according to any one of claims 1 to 16, comprising a plurality of identical or different layers (multilayers). 18. The method according to claim 17, wherein the sulfonated polyether ketone and aminated polyether sulfone, sulfonated polyether ketone and nitrated polyether sulfone, sulfonated polyether ketone and aminated polyether sulfone and plasticizer, sulfonated polyether ketone and A membrane comprising at least two different layers selected from the group consisting of nitrated polyether sulfones and plasticizers. Use of the membrane as claimed in any one of claims 1 to 18 for producing a membrane electrode unit (MEA) of a fuel cell, in particular a low temperature fuel cell having an operating temperature of 10 ° C to 200 ° C. A fuel cell comprising the polymer electrolyte membrane as claimed in claim 1.